Apparatus for piecing-up yarn in an open-end-spinning device

ABSTRACT

A momentary contact switch connected in parallel with a yarn tension monitoring switch is actuated by swinging of the bobbin holder beyond a normal servicing position immediately prior to swinging such holder into working position. Such switch overrides the yarn-monitoring switch to effect fiber feed to the yarn formation zone earlier than such feed would normally be effected by the yarn-monitoring switch since the latter switch is not actuated until the yarn tension is increased to normal spinning tension. A holding switch is actuated by the momentary contact switch to maintain the overriding function between the time the momentary contact switch is released by the bobbin holder being swung out of contact and the time the yarn-monitoring switch is reversed. Alternatively, a Bowden wire connecting the bobbin holder and the yarn-monitoring switch reverses such switch to begin fiber feed. Other overriding switch constructions include a button on the bobbin holder manually operable to release the bobbin holder from a latched servicing position and simultaneously to actuate the overriding switch, a swingable switch lever moved into and out of switch-actuating contact with a leaf spring contact as a cam slides past it on opposite passes of the swinging bobbin holder, or a ratchet-and-pawl latch for the bobbin holder in which the pawl constitutes a switchactuating cam.

United States Patent [191 Landwehrkamp et a1.

[ APPARATUS FOR PlEClNG-UP YARN IN AN OPEN-END-SPINNING DEVICE [75] Inventors: Hans Landwehrkamp, Gerolfing;

Gerhard Hoeber, lngolstadt, both of Germany [73] Assignee: Schubert & Salzer Masehinenfabrik Aktiengesellschaft, lngolstadt, Germany [22] Filed: Nov. 18, 1971 [2]] Appl. No.: 200,125

[30] Foreign Application Priority Data Nov. 28, 1970 Germany P 20 58 603.2

[52] 11.5. C1. 57/34 R, 57/58.95, 57/81, 57/83 [51] Int. Cl. D0lh 15/00, DOlh 13/18 [58] Field of Search 57/34 R, 78, 58.89-58.95, 57/22, 23, 80, 81, 85, 159; 242/39, 35.5

Jan. 1, 1974 Primary Examiner.lohn Petrakes Assistant Examiner-Charles Gorenstein AttorneyRobert W. Beach [5 7 1 ABSTRACT A momentary contact switch connected in parallel with a yarn tension monitoring switch is actuated by swinging of the bobbin holder beyond a normal servicing position immediately prior to swinging such holder into working position. Such switch overrides the yarnmonitoring switch to effect fiber feed to the yarn formation zone earlier than such feed would normally be effected by the yarn-monitoring switch since the latter switch is not actuated until the yarn tension is increased to normal spinning tension. A holding switch is actuated by the momentary contact switch to maintain the overriding function between the time the momentary contact switch is released by the bobbin holder being swung out of contact and the time the yarn-monitoring switch is reversed. Alternatively, a Bowden wire connecting the bobbin holder and the yarn-monitoring switch reverses such switch to begin fiber feed. Other overriding switch constructions include a button on the bobbin holder manually operable to release the bobbin holder from a latched servicing position and simultaneously to actuate the overriding switch, a swingable switch lever moved into and out of switch-actuating contact with a leaf spring contact as a cam slides past it on opposite passes of the swinging bobbin holder, or a ratchet-and-pawl latch for the bobbin holder in which the pawl constitutes a switch-actuating cam.

11 Claims, 6 Drawing Figures 1 APPARATUS FOR PIECING-UP YARN IN AN OPEN-END-SPINNING DEVICE BACKGROUND OF INVENTION 1. Field to which invention relates The present invention relates to an apparatus for piecing-up yarn in an open-end-spinning device with a controlled fibre supply means, a spool device with a tilting spool holder provided with the handle and a yarn monitoring device arranged to control the fibre supply means and arranged between a yarn formation zone and the spool device.

2. The prior art In accordance with a previously proposed method, the drawoff of yarn from the spinning apparatus is arranged to be stopped as rapidly as possible when a yarn breakage occurs in response to a feeler so that the yarn end remains in the spinning apparatus (see British patent specification No. 1,158,623). Piecing-up is then immediately carried out automatically and the fibre supply does not have to be interrupted.

It, however, may occur that the yarn end nevertheless leaves the spinning apparatus so that automatic piecing-up is not possible. Furthermore, idle periods for servicing, such as for cleaning the spinning apparatus or for other reasons, make it necessary for spinning to be started with manual aid. In this case the spool or bobbin is raised from its drive and the operator locates the yarn end and introduces it with one hand into the drawofi' tube while the other hand is used to hold the yarn loop. The operator then lowers the spool or bobbin somewhat and at the same time releases the yarn loo'p. As soon as the latter is drawn back by the suction into the spinning apparatus the yarn monitoring means is actuated and the latter controls the fibre supply apparatus. Thus the supply of new fibres to the spinning apparatus is started and the yarn comes into contact with the newly supplied fibres. The spool is then lowered as far as the winding roller and the normal spinning process can then proceed.

The disadvantage of this method is to be found in that the supply of new fibres can only start when the yarn end has been drawn by suction back into the spinning apparatus and thus actuates the yarn monitoring means. This brings with it the danger that the yarn end may be drawn out of the spinning apparatus before sufficient fibres have been fed into the spinning apparatus. Attachment or piecing-up can then not be carried out and the operation for starting spinning must be repeated.

There has been a further prior proposal to switch on the fibre supply device before the feeding back of the yarn as far as the yarn formation zone (see Swiss patent specification No. 457,221). If, however, within a certain period of time following the switching on of the spinning apparatus the yarn end does not come into contact with the newly fed-in fibres there is a danger of blocking of the spinning apparatus. The success of the piecing-up operation is thus to a high degree dependent on the skill of the human operator.

SUMMARY OF INVENTION In order to facilitate this piecing-up operation, one aim of the invention is to provide an apparatus which makes possible the individual switching-on of the fibre supply device in a simple manner and is particularly designed to suit the hand operations involved in starting spinning manually.

The present invention consists in an apparatus for piecing-up yarn in an open-end-spinning device comprising a controlled fibre supply means, a spool device with a tilting spool holder provided with the handle, a yarn monitoring device arranged to control the fibre supply means and arranged between a yarn formation zone and the spool device, an actuator arranged on the bobbin holder, and a switch connected with the fibre supply device and being arranged to be controlled by the actuator. In this respect the switch can be formed by the yarn monitoring means which for this purpose is provided with a tilting drive capable of being actuated by the actuator. As an alternative feature the switch can be arranged in a parallel circuit containing the yarn monitoring means. Since, for releasing the yarn end to be returned, the bobbin or spool must be removed from the winding roller by swinging the bobbin holder, the switch can be arranged in the path of tilting of the bobbin holder and the switching part can be constructed as a drive cam which is provided on the bobbin holder and can be brought into a position for cooperation with the switch. Advantageously the operating cam can be arranged laterally on the bobbin holder, and an intermediate lever can be provided which can be swung in both tilting directions of the bobbin holder by the action of the operating cam. This intermediate lever only actuates the switch during the downward movement of the bobbin holder and for this purpose is provided with an elastic member. In order to ensure that the operator only has to tilt the bobbin holder and does not have to hold it in the raised position a non-rotary ratchet wheel can be provided on the pivot pin of the bobbin holder and on the bobbin holder itself a driven pawl is provided. In order to avoid the necessity of complicated operations for releasing the pawl, the ratchet wheel can be provided with a blanking part or stop which can be twisted by the pivoting movements of the bobbin or spool holder and can be twisted between two stationary abutments. If the switch is in the upper tilting path of the bobbin holder, the pawl can furthermore be constructed as an operating cam for the switch.

In order to ensure that the actuation of the switch is independent from the tilting operation, the switch part is preferably arranged on the handle of the bobbin holder. The switch part can simultaneously serve for actuating the pawl and in this case is mechanically connected with the latter. In accordance with a particularly compact construction the switch can be arranged in the spool or bobbin holder. The apparatus in accordance with the invention enables that hand which holds the bobbin holder to be used to switch-on the fibre supply device at the desired point in time so that fibre supply only starts when the operator wishes it. In this manner piecing-up can be carried out individually without the operator having to keep to the switching-on speed determined by the automatic switching-on means.

Further details of the invention will now be described with reference to some embodiments which are shown in the accompanying drawings. Only those parts relevant for gaining an understanding of the invention are shown.

LIST OF SEVERAL VIEWS OF DRAWINGS FIG. 1 shows diagrammatically an open-end-spinning device with the piecing-up apparatus in accordance with the invention.

FIG. 2 shows a diagrammatic front elevation of a further form of the subject matter of the invention.

FIGS. 3 to 5 show details of the bobbin holder in section and in side view.

FIG. 6 shows a further embodiment of the apparatus in accordance with the invention.

For the present invention the exact nature of the yarn building zone is not important. The yarn can be formed in a spinning turbine, a rotating or stationary spinning funnel or as a chamber in which fibres moved in a medium are laid against a freely rotating yarn end.

FIG. 1 shows a spinning device with such a yarn formation zone 1, to which the fibres are supplied by a fibre supply device 2. Adjacent to the yarn outlet opening 10 of the drawoff tube from the yarn formation zone 1, there is a yarn monitoring device 3, which is connected for cooperation with a control device for the fibre supply device 2 and monitors the yarn tension of the yarn ll drawn off by a drawoff device (not shown) or a bobbin device 4. The bobbin device 4 has a driven winding roller 40 and a bobbin 41, which are carried by a pair of bobbin holders 42 engaging opposite ends of the bobbin so as to allow replacement. The bobbin holders 42 have a handle 43, by means of which they can be raised from the winding roller 40. When this is carried out, the bobbin holders 42 are swung about a pin or shaft 44. On the upper side of at least one of the two bobbin holders 42 there is an operating or switching part in the form of an actuating cam 45 which in the upper position of the bobbin holder 42 acts on a switch 5. This switch 5 is arranged in a circuit in parallel to the yarn monitoring device 3 so that the yarn monitoring device can be bypassed by the switch 5. In order for the supply of current to the control device 20 not to be interrupted immediately after release of the switch 5 there is in this parallel circuit a relay 50 which holds itself with the help of a contact 51 until the yarn monitoring device 3 constructed as a reversing switch resumes the supply of current to the control device 20 of the fibre supply device.

The apparatus described above operates in the following manner.

After the switching-on program has been started by actuation of the main switch, the operator takes the yarn end'with one hand, possibly after having removed a length of yarn which cannot be used for piecing-up. With the other hand he or she lifts the bobbin holder 42 clear of the winding roller 40 so that he or she can draw off the necessary length of yarn from the spool or bobbin 41. The end of the yarn 11 is then introduced into the exit opening 10 of the yarn building zone 1. At the same time the spool or bobbin holder 42 is raised so far that the switch 5 is closed. As a result the relay 50 is excited and closes a contact 51 and thus holds itself in the switched-on condition. The control device 20 of the fibre supply device is in this manner supplied with current via the switch 5 and the relay 50 and later via the contact 51 and the relay 50 and via the yarn monitoring device 3, which is in the position shown in full lines, so that the yarn formation zone 1 is supplied with fibres. The operator now lowers the bobbin holder 42, which thus comes into engagement with the winding roller 40. The yarn 11, which in the meantime has made contact with the fibres freshly fed into the yarn formation zone 1, is now drawn out of the yarn formation zone 1 again. Owing to the restoration of normal yarn tension the yarn monitoring device 3 is switched over into the position shown in broken lines and the relay 50 is opened. The fibre supply device 2, however, remains switched on via the yarn monitoring device 3. Thus, the piecing-up operation is at an end.

. The subject matter of the invention can be embodied in various different ways. FIG. 6 shows a different embodiment of the device in accordance with the invention, in which a switching circuit is also closed by the tilting movement of the bobbin holder 42. The switching or operating part in this case is in the form of an operating cam 45' which is, however, arranged to the side on the bobbin holder 42. The operating cam 45 cooperates with a two-armed intermediate lever 52 which is attached in a pivoting manner to a shaft or pin 53 carried by the machine frame 12. The longer arm of the intermediate lever 52 is located between two elastic members which may, for example, be in the form of strip springs 54 and 55 as in the present case. The strip springs are attached to a holder 56 and insulated electrically from each other. The strip spring 54 and the machine frame 12 or at least the shaft 53 and the lever 52 are connected via leads 57 and 58 so as to be in parallel electrically with the yarn monitoring device 3 as shown in FIG. 1.

The two-armed intermediate lever 52 is, as already mentioned, eccentrically journalled, and its basic position is as shown in broken lines (52'). In this position its longer arm lies on the strip spring 55. On raising the bobbin holder 42 the operating cam 45'. acts on the shorter arm of the intermediate lever 52 to swing it in an counterclockwise direction until it comes into the position 52" indicated in dot-dash lines. In this position the operating cam 45' can pass by the intermediate lever 52 which, with the help of the strip spring (position shown in broken lines 55') cocked by the swinging of the intermediate lever 52, is swung back into the basic position (52'). There is thus no switching operation in the case of upward movement of the bobbin holder. In the case of downward movement of the bobbin holder 42, on the other hand, the intermediate lever 52 is brought into the positionshown by the full line. In this position the intermediate lever 52 comes to lie against the strip spring 54. Thus, current can flow from the line 58 via the intermediate lever 52 and the strip spring 54 to the line 57 and from this position it can flow to the control device 20 of the fibre supply device. Consequently, lever 52 constitutes a switching lever and strip 54 is the switch-closing contact. In the case of further downward movement of the spool or bobbin holder 42, the operating cam 45 swings the intermediate lever 52 into the position 52' indicated in dotted lines and the strip spring 54 moves out of the way into the position 54. After release by the operating cam 45' the intermediate lever 52 returns into its basic position 52 owing to its eccentric bearing and the control device 20 remains switched on by the relay 50.

Naturally in this respect as well other designs are possible. For example, a single-armed lever in its basic position can be prevented by an elastic member from actuating an end switch (not shown) arranged below of its basic position. Owing to the downward movement of the bobbin holder 42 this end switch is actuated by a lever swung against the action of the elastic member and the lever returns into its basic position on release by the operating cam 45.

In order to facilitate the work of the operator it is possible to provide on the shaft or pin 44 of the bobbin holder 42 a non-rotary ratchet wheel 6 rigidly fixed to the pin 44 (see FIG. 3). On the bobbin holder 42 a controlled pawl 60 is provided which is held by a compression spring 61 in engagement with the ratchet wheel 6. The pawl 60 is so constructed and arranged that it extends at least partially laterally beyond the path of tilting movement of the bobbin holder 42. The bobbin holder in this case is preferably in the form of a sleeve 46. The end of this sleeve remote from the pin 44 serves as a handle, in which a sliding shoe 62 constructed as an operating part is guided. The sliding shoe has a plate-like broadened portion 63 outside the sleeve 46 in order to allow the operator to pull the sliding shoe 62 out of the sleeve 46. For limiting the stroke of the sliding shoe 62 an abutment 64 is provided which is attached to a pin 65. This pin is guided in a hole 66 of the sliding part'62 and is attached by means of a pin 67 to the sleeve 46. Furthermore, the pawl 60 is connected by means of a pull rod 68 with the sliding shoe 62.

On raising the bobbin holder 42 the ratchet pawl 60 is caused by the compression spring 61 to engage the ratchet wheel 6 and holds the bobbin holder 42 in the position which it has assumed. For lowering the bobbin holder 42 and for actuating the switch the operator uses his or her index and middle fingers of the hand holding the bobbin holder 42 to draw the sliding shoe with the help of the plate-like broadened portion 63 until it strikes the abutment 64, while the .thumb of the operator rests on the abutment 64. Thus, the pawl 60 releases the ratchet wheel 6 and simultaneously operates(see position 60') the switch 5, so that the control device is switched on for the fibre supply device in the manner already described. The pawl 60 thus simultaneously constitutes the operating cam for the switch 5. The bobbin holder 42 can now be lowered for piecing-up.

In the construction in accordance with FIGS. 1 and 6, in which there is no latching part in the handle 43, it is possible to provide a ratchet wheel 6 and a controlled pawl 60 such as shown in FIG. 5. For this purpose a stop or blanking part 7 is provided on the shaft or pin 44 and can be swung about such pin (FIG. 5) by the action of the compression spring 61 engaging the pawl 60. Two abutrnents 70 and 71 are rigidly fixed to the pin 44 and preferably form the ends of a common ring section. On raising the bobbin holder the pawl 60 conjointly swings the stop or blanking part 7 in a counterclockwise direction due to frictional engagement of the complemental surfaces of pawl 60 and part 7 and the force of compression spring 61 urging the members 60 and 7 together. The tip of pawl 60 projects beyond stop 7 to slide along the backs of the ratchet teeth. Before the upper end position is reached, the pawl 60 snaps into the ratchet 6 wherever it is stopped and holds the spool or bobbin holder 42 in the position it has assumed. On further raising the stop 7 abuts against the abutment 70 so that the pawl 60 slides onto the stop 7 and is thus brought out of engagement with the ratchet wheel 6. The bobbin holder can thus be lowered and, again, frictional engagement between them will cause the pawl 60 and member 7 to swing downward conjointly so that the tip of the pawl remains out of engagement with the ratchet wheel 6. Shortly before reaching the lower end position of the spool holder 42 the stop 7 strikes against the lower abutment 71 while the bobbin holder 42 is lowered further. Thus, the pawl 60 slides past member 7 sufficiently so that its tip comes into engagement with the ratchet wheel 6 again.

The switch can also be arranged in the bobbin holder. FIG. 4 shows the sleeve 46 of a bobbin holder 42 whose end remote from the shaft 44 forms the handle of the bobbin holder. An electrically non-conducting sleeve 8 having an inner closed end is screwed into such end of the bobbin holder. Contact springs are mounted in the sleeve inner closed end and are connected with the leads 57 and 58. A switch operating button 81 mounted in the open end of sleeve 8 has an outward projection and is pressed outwards by a compression spring 82 reacting between the end wall of the sleeve 8 and the button 81. The operating button 81 is held in the sleeve 8 by a cap nut 83 screwed onto the sleeve 8. The cap nut 83 includes an outwardly projecting annular flange. On the side adjacent to the contact springs 80 the operating button 81 carries an operating ring 84 which connects the two contact springs 80 with each other when the operating button 81 is actuated. Furthermore, a pin or bolt 85 is screwed into the operating button 81 and is guided by a hole 86 in the end wall of the sleeve 8 and in a hole 87 of a guide disc 88 arranged in the sleeve 46. The pin 85 rests against the one arm of the pawl 60. The latter is in this case constructed as a two-armed lever and is held again in engagement with the ratchet wheel 6 by a compression spring 61. For releasing the ratchet wheel 6 and for connecting the contact springs 80 by the operating ring 84 the actuating button 81 is actuated. In other respects the function is as described above. On releasing the operating button 81 the latter returns into the basic position shown owing to the action of the compression spring 82 and the flow of current between the contact springs 80 is interrupted. Simultaneously the pawl 60 comes into engagement with the ratchet wheel 6 again.

Owing to the fact that the switch formed by the contact springs 80 and the operating ring 84 is accommodated in the bobbin carrier 42, a particularly compact construction in accordance with the invention is provided.

It is not necessary for the switch to be arranged in a circuit parallel to the yarn monitoring device. Instead the switch can be formed by the yarn monitoring device 30 itself. Such an embodiment is shown by FIG. 2. On the handle 43 of the bobbin holder 42 an operating part in the form of an operating lever 31 is provided, which is held in its basic position by a spring (not shown). A Bowden cable 32 is connected with the operating lever 31 and with a pivoting drive 33 for the feeler 34 of the yarn monitoring device 30. If the control device 20.for the fibre supply device 2 is to be switched on for piecing-up, the operating lever 31 is actuated and brings via the Bowden cable 32 and the tilting drive 33 the feeler 34 of the yarn monitoring device 30 out of the position 34' shown in broken lines into the position 34 shown in full lines.

The invention, of which only a few embodiments have been described, makes it possible to switch-on the fibre supply device in a simple manner at a desired point in time so that the quantity of fibre necessary for piecing-up in the yarn formation zone 1 will be available when required. Since the operating part is arranged on the bobbin holder 42, the operator can swing the bobbin holder 42 and operate the operating part simultaneously with one hand.

Although the apparatus in accordance with the invention has not been described in conjunction with draw-off rollers, such drawoff rollers can nevertheless be provided. During the piecing-up of the yarn the latter is not in the nip line of the drawoff roller pair and is only drawn into the nip line after the termination of the piecing-up operation.

We claim:

1. An apparatus for piecing-up yarn in an open-endspinning device comprising a yarn formation zone, separating means for separating a fibre band into individual fibers, feeding means for feeding a fiber band to said separating means including control means for controlling feed of the fiber band, a spool device for receiving a yarn having been spun in said yam formation zone having a swingable bobbin holder, a handle on said bobbin holder to swing said bobbin holder between a working position and a servicing position, yarnmonitoring means between said yarn formation zone and said spool device electrically connected to said control means for operating said control means in response to yarn tension to stop fiber band feed when such tension is reduced below a selected tension and to permit such feed when the tension exceeds such selected tension, means for overriding operation of said control means by said yarn-monitoring means, and an operating part on said bobbin holder for actuating said overriding means in response to selected movement of said bobbin holder to effect fiber band feed irrespective of the feed-stopping condition of said yam-monitoring means.

2. Apparatus defined in claim 1, in which the yarnmonitoring EFaFs iHETUHETa swmiamer niovable between a first position in which said member supplies current to the control means to permit fiber feed and a second position in which said member interrupts supply of current to the control means for stopping the fiber band feed, and the overriding means is operable to move said switching member into the first position.

3, An apparatus for piecing-up yarn in an open-endspinning device comprising a yarn formation zone, separating means for separating a fiber band into individual fibers, feeding means for feeding said fiber band to said separating means, control means for controlling feed of the fiber band, a spool device for receiving a yarn having been spun in said yarn formation zone having a swingable bobbin holder, a handle on said bobbin holder to swing said bobbin holder between a working position and a servicing position, yarn-monitoring means between said yarn formation zone and said spool device for monitoring yarn tension, an electrical connection circuit for interconnecting said yarnmonitoring means and said control means, said yarnmonitoring means operating said control means in response to said yarn tension to stop fiber band feed when such tension is reduced belowa selected tension and to pennit such feed when the tension exceeds such selected tension, and overriding means comprising a switch connected in parallel to said yarn-monitoring means in said electrical connection circuit operable by swinging of the bobbin holder, to override the operation of said control means by said yarn monitoring means.

4. The apparatus defined in claim 3, in which said switch is located in the swinging path of the bobbin holder, furtherincluding a switch-operating part having a cam carried on the bobbin holder, said cam being engageable with the switch.

5. The apparatus defined in claim 3, further including a switch-operating cam projecting from the bobbin holder in a direction substantially perpendicular to the plane through which the bobbin holder is swingable,

the switch being located in the swinging path of said cam and including a contact, an intermediate lever which can be tilted in a first direction by said cam to engage said switch contact during downward movement of the bobbin holder and a second direction away from said contact, said contact being an elastic member.

6. The apparatus defined in claim 3, further including a pivot pin about which the bobbin holder is swingable, a stationary ratchet wheel carried by said pivot pin, and a control pawl carried on the bobbin holder and engageable with said ratchet wheel for holding the bobbin holder in a swung position.

7. The apparatus defined in claim 6, further including astop swingable with the bobbin holder andengageable by the pawl to hold such pawl out of engagement with the ratchet, two stationary abutments engageable by said stop spaced arcuately relative to the ratchet a distance less than the arcuate extent of maximum pawl travel, the pawl being slidable relative to said stop when said stop is engaged with one of said abutments in response to further swinging of the bobbin carrier.

8. The apparatus defined in claim-6, in which the pawl is engageable with the switch for actuation thereof.

9. The apparatus defined in claim 3, further including an operating part carried on the handle of the bobbin holder for actuation of the switch.

10. The apparatusdefined in claim 9, in which the operating part is mechanically connected with the pawl.

11. The apparatus defined in claim 9, in which the overriding means includes a switch carried by the bobbin holder. 

1. An apparatus for piecing-up yarn in an open-end-spinning device comprising a yarn formation zone, separating means for separating a fiber band into individual fibers, feeding means for feeding a fiber band to said separating means including control means for controlling feed of the fiber band, a spool device for receiving a yarn having been spun in said yarn formation zone having a swingable bobbin holder, a handle on said bobbin holder to swIng said bobbin holder between a working position and a servicing position, yarn-monitoring means between said yarn formation zone and said spool device electrically connected to said control means for operating said control means in response to yarn tension to stop fiber band feed when such tension is reduced below a selected tension and to permit such feed when the tension exceeds such selected tension, means for overriding operation of said control means by said yarn-monitoring means, and an operating part on said bobbin holder for actuating said overriding means in response to selected movement of said bobbin holder to effect fiber band feed irrespective of the feedstopping condition of said yarn-monitoring means.
 2. The apparatus defined in claim 1, in which the yarn-monitoring means includes a switching member movable between a first position in which said member supplies current to the control means to permit fiber feed and a second position in which said member interrupts supply of current to the control means for stopping the fiber band feed, and the overriding means is operable to move said switching member into the first position.
 3. An apparatus for piecing-up yarn in an open-end-spinning device comprising a yarn formation zone, separating means for separating a fiber band into individual fibers, feeding means for feeding said fiber band to said separating means, control means for controlling feed of the fiber band, a spool device for receiving a yarn having been spun in said yarn formation zone having a swingable bobbin holder, a handle on said bobbin holder to swing said bobbin holder between a working position and a servicing position, yarn-monitoring means between said yarn formation zone and said spool device for monitoring yarn tension, an electrical connection circuit for interconnecting said yarn-monitoring means and said control means, said yarn-monitoring means operating said control means in response to said yarn tension to stop fiber band feed when such tension is reduced below a selected tension and to permit such feed when the tension exceeds such selected tension, and overriding means comprising a switch connected in parallel to said yarn-monitoring means in said electrical connection circuit operable by swinging of the bobbin holder, to override the operation of said control means by said yarn monitoring means.
 4. The apparatus defined in claim 3, in which said switch is located in the swinging path of the bobbin holder, further including a switch-operating part having a cam carried on the bobbin holder, said cam being engageable with the switch.
 5. The apparatus defined in claim 3, further including a switch-operating cam projecting from the bobbin holder in a direction substantially perpendicular to the plane through which the bobbin holder is swingable, the switch being located in the swinging path of said cam and including a contact, an intermediate lever which can be tilted in a first direction by said cam to engage said switch contact during downward movement of the bobbin holder and a second direction away from said contact, said contact being an elastic member.
 6. The apparatus defined in claim 3, further including a pivot pin about which the bobbin holder is swingable, a stationary ratchet wheel carried by said pivot pin, and a control pawl carried on the bobbin holder and engageable with said ratchet wheel for holding the bobbin holder in a swung position.
 7. The apparatus defined in claim 6, further including a stop swingable with the bobbin holder and engageable by the pawl to hold such pawl out of engagement with the ratchet, two stationary abutments engageable by said stop spaced arcuately relative to the ratchet a distance less than the arcuate extent of maximum pawl travel, the pawl being slidable relative to said stop when said stop is engaged with one of said abutments in response to further swinging of the bobbin carrier.
 8. The apparatus defined in claim 6, in which the pawl is engageable with the switch fOr actuation thereof.
 9. The apparatus defined in claim 3, further including an operating part carried on the handle of the bobbin holder for actuation of the switch.
 10. The apparatus defined in claim 9, in which the operating part is mechanically connected with the pawl.
 11. The apparatus defined in claim 9, in which the overriding means includes a switch carried by the bobbin holder. 